Split cylindrical transducer



Nov. 5, 1957 5 w. 'r. HARRIS SPLIT CYLINDRICAL TRANSDUCER Filed May 22, 1956 m m m m HTZ'OEA/EVS 2,812,452 $1 1.11 CYLINDRICAL TRANSDUCER Wilbur Harris, Southbury, Conn., assignor to The Harris Transducer Corporation, Woodbury, Conn., a corporation of Connecticut Appiication May 22, 1956, Serial No. 586,501 13 Claims. (Cl. 310-8.2)

My invention relates to an improved electroacoustic transducer construction having particular application to underwater radiation where a high power-to-weight ratio is of extreme importance, as for example, in helicopterdunked applications.

It is an object to provide an improved device of the character indicated. y

it is another object to provide an improved underwater acoustic radiating transducer featuring extreme simplicity and ruggedness.

it is also an object to meet the above objects with a construction inherently capable of essentially omnidirectional radiation, as throughout a horizontal plane.

it is a further object to provide an improved basic transducer-element configuration lending itself to a plurality of various array configurations depending upon the overall response desired.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. l is a simplified view in perspective with certain parts broken away to reveal internal construction of a transducer of my invention; 1

Fig.2 is an enlarged sectional view, taken in the plane 2-2 of Fig. 1; i e

Fig. 3 is a view similar to Fig. 1, but showing a modification; and y Figs. 4, 5 and 6 are further views in perspective showing alternative array utilizations of the basic transducer element of Fig. l or 3.

Briefly stated, my invention contemplates a basic transducer element comprising essentially two 'coaxially interfitting cylindrical members bonded to each other and longitudinally split at essentially a single angular location. One of the tubular members is a metal support, and the other tubular member is a piezoelectric motor element. In the forms to be described, the piezoelectric motor element is contained within the metal tube, and support for the assembly is provided essentially along a line diametrically opposite the slit location, as by brazing the support member to the outer metal tube of the transducer element. Various array configurations for the basic transducer element areshown and described.

Referring to Figs. 1 and 2 of the drawings, my invention is shown in application to a composite cylindrical transducer element 10 comprising an outer metal tube or cylinder 11, as of steel or aluminum, and an inner tube or cylinder 12, constituting a piezoelectric motor element. The two cylinders 11-12 are substantially coextensive and are bonded throughout, as by means of an'epoxy resin; both cylinders 11-12 are slitted or split at 13 along aline at essentially asingle angular location, Support for the element 10 may be provided bya rigid elongated metal base member or support 14, which is shown as a tube closed at both ends,'as by merelyflattenin'g' at 15-16 to provide securing means 17-12} for mounting purposes. The support 14 is in the form shown secured to the metal cylinder'll along essentially a line diametrically opposite the slit 13, and in Fig. 2 elongated brazing connections" are suggested at' 19-20.

States Patent o The piezoelectric motor element may comprise a piezoelectric core 21, as of barium titanate, and carrying two foil electrodes 22-23 on the inner and outer surfaces thereof. The core 21 will be understood to be polarized in the usual manner so that alternating electric voltage applied across the'electrodes 22-23 will mechanically stress the core 21 to produce expanding and contracting generally radial movements of the opposed tynes or arms,

designated generally 24-25. The piezoelectric motor 12' may be bonded to the metal cylinder 11 with plastic, solder, or enamel, and the composite assembly may be dipped in enamel or plastic to provide the coating 26 over ail exposed surfaces.

Electric-lead connections are established to a supply cable 27 which may be conveniently accommodated within the support 14. Because one electrode (22) of the piezoelectric motor 12 is electrically connected to the metal cylinder 11 and thus to the support 14, a ground lead 28 may merely be connected to the support 14. The remaining lead 29 may pass through an insulated bushing 30 adjacent one supported end of the transducer unit it and the necessary electrical connection made directly to the inner foil electrode 23, as best shown in Fig. 1. To complete the assembly, the interior of the support 14 may be potted in a suitable incompressible plastic.

For certain applications, it is desirable to provide a pressure-release mechanism within the tubular transducer unit 10, and in Fig. 3 I illustrate how such provision may be conveniently made. For convenience, parts common to both Figs. 1 and 3 have been given the same reference numerals in both cases. Actually, pressure release within the transducer unit 10 may be very simply provided by employment of air-filled rubber or the like, but in Fig. 3 I illustrate my preference for a more rugged pressure-release member 32, which is shown to comprise an elongated flattened relatively thin-walled tube of metal closed at both ends, as by squeezing to form mounting lugs 33-34; the pressure-release length of member 32 is thus preferably of generally oval section.

The pocket defined within the pressure-release tube 32 may contain merely air, or it may be filled with an airfilled rubber or the like. Simple standards 35 carried by the base 14 adequately position and hold the respective ends 33-34 of the pressure-release member.

- In operation, the horseshoe-shaped device vibrates something like a tuning fork when A.-C. voltage is applied, and for this characteristic mode, the composite split cylinder is a high-Q resonant structure. The'rnotion of the centers of vibration on either side of the diametral plane of the split has a component normal to said plane and a component parallel to said plane. Therefore, in operation, any single composite cylindrical device has a small resultant component of force or motion which would be communicated to the base or holder 14. Such force or motion is suggested by the arrow 38 in Fig. 2.

In Fig. 4, I illustrate one form of array configuration to which my basic transducer element, be it of the form of Fig. 1 or that of Fig. 3, is inherently applicable. In Fig. 4, a single elongated tubular support member 40 serves a plurality of longitudinally spaced transducer elements 41-42. The tube 49 will be understood to carry a single lead cable 43, and all necessary individual canducers are excited in unison.

nections, as at 44-45, maybe made from base 40 to the respective transducer elements. Because each transducer element 41 or 42 functions with a slight residual The arrangement of Fig. 5 illustrates a further modification wherein the plurality of angularly spaced transducer units exceeds two. Depending upon the size of the support member 50, compared with the diameter of the individual transducer elements (such as that of the element 51), almost any desired plurality of elements 51 can be bonded to and spaced around a given support member 50. In every case, the slit openings (as at 52) will face outwardly of the support 50, so that all reacting forces will be directed at the axis of the support 50. In the arrangement of Fig. 5, three equally angularly spaced transducer units 51 53--54 are shown, and if the device is supported with the axis of base 50 oriented vertically, generally omnidirectional response in the horizontal plane will be achieved.

In the arrangement of Fig. 6, I show an array of like transducer assemblies, each of which comprises a central support, as at 60-, and two diametrically opposed transducer elements 6162. For the fragment shown in Fig. 6, the assemblies 63-64 duplicate the assembly 6tl- 6162, and frame means 6566 serve to interconnect the corresponding longitudinal ends of the support memers (60) for all transducer assemblies. In the arrangement shown, the frame means 65-66 maintains the axes of all composite cylinders in substantially parallel relation; for any particular transducer assembly (e. g. 63), the plane which includes both cylinder axes is spaced from and generally parallel to the corresponding plane of the adjacent transducer assembly.

It will be seen that I have described an improved basic transducer construction lending itself particularly to use in array configurations in a manner to neutralize reaction forces. My device is inherently characterized by a high power-to-weight ratio, and yet the structure is sufliciently rugged to Withstand substantial abuse.

While I have described the invention in detail for the preferred forms illustrated, it will be understood that modifications may be made within the scope of the invention, as defined in the claims which follow.

I claim:

1. In a transducer of thecharacter indicated, an elongated metal tubular member having a single continuous slit at one angular location, support means rigidly tied to said cylinder at a location substantially diametrically opposite the location of said slit, whereby opposite halves of said cylinder constitute tynes of a tuning fork, and piezoelectric element means bonded to and carried by each of said tynes.

2. In a transducer of the character indicated, two coaxially interfitting cylindrical members bonded to each other and slit longitudinally at the same angular location, one of said members being of metallic tubing, and the other of said members being a piezoelectric transducer element, said element comprising inner and outer foil electrodes bonded to a cylindrical piezoelectric core.

3. In a transducer of the character indicated, an elongated metal tube, an elongated tubular piezoelectric transducer element substantially coextensive with said tube and bonded to the inner surface thereof, said metal tube and said transducer element being slitted longitudinally as essentially the same angular location, and rigid support means secured to said metal tube at a location substantially diametrically opposite the location of said slit.

4. In a transducer of the character indicated, an elongated metal tube, an elongated tubular piezoelectric transducer element substantially coextensive with said tube and bonded to the inner surface thereof, said metal tube and said transducer element being slitted longitudinally at essentially the same angular location, rigid support means secured to said metal tube at a location substantially diametrically opposite the location of said slit, and elongated pressurearelease means carried by said support and positioned generally centrally of said transducer element.

5. A transducer according to claim 4, in which said pressure-release means comprises an elongated metallic tube closed at both ends to define a sealed pressurerelease volume, said pressure-release volume being substantially coextensive with. said transducer element.

6. A transducer according to claim 5, in which said tube is of relatively thin-walled generally oval section and is air-filled.

7. In a transducer of the character indicated, an elongated metal tube and an elongated tubular piezoelectric transducer element substantially coextensive with said tube and bonded to the inner surface thereof, said metal tube and said transducer element being slitted longitudinally at essentially the same angular location, rigid support means secured to said metal tube at a location substantially diametrically opposite the location of said slit, said support comprising an elongated metal tube closed at both ends, the axis of saidsupport tube being parallel to the axis of said transducer element, and said support tube being secured to said slit metal tube essentially along a line in the diametral plane including said slit.

8 A transducer according to claim 7, and including lead-in supply means for said piezoelectric element and contained within said support tube, said lead-in supply means being potted in said support tube.

9. In combination, an elongated metal support, and a plurality of longitudinally slitted composite cylindrical transducer elements secured to said support at substantially equally angularly spaced locations around said support, each said transducer comprising a cylinder of piezoelectric material bonded within a metal cylinder, each transducer element being slitted at one angular location, said metal cylinder being secured to said support along a line in the diametral plane of said transducer element which includes said slit.

10. In combination, an elongated metal support member and a plurality of like elongated transducer assemblies secured in longitudinally spaced relation to said support member, each transducer element comprising an outer cylinder of metal and an inner cylindrical piezoelectric motor element, each transducer being longitudinally slitted at essentially one angular location and being secured to said support at a diametrically opposite location.

11. The combination according to claim 10, in which said support is a tube closed at both ends and contains lead-in connections toall said transducers.

12. In combination, an array of like transducer assemblies, each said assembly including a common metal tubular support and two split composite cylindrical transducers secured to said support at diametrically opposite locations, each transducer comprising an outer metal tube and a cylindrical piezoelectric motor element bonded to the inner surface of said metal tube, said transducers being secured to said support With the splits thereof facing outwardly of said support.

13. In combination, an array of like transducer assemblies, each said assembly including a common metal tubular support and two split composite cylindrical transducers secured to said support at diametrically opposite locations, each transducer comprising an outer metal tube and a piezoelectric cylindrical motor element bonded to the inner surface of said metal tube, said transducers being secured to said support with the splits thereof facing outwardly of said support, and frame means interconnecting corresponding longitudinal ends of said supports and orienting the axes of all transducer elements in substantially parallel relation.

References Cited in the file of this patent UNITED STATES PATENTS 

